A standard apparatus for unloading bulk material from a ship or the like has a portal-type carriage or support that can normally move longitudinally on a dock or pontoons along the normally fixed ship and that carries an outrigger or boom having an inner end pivoted on the support and a vertically movable outer end positionable above the ship to be unloaded. A pendant arm has an upper end pivoted on the outer end of the outrigger and a lower end that can be dipped down into the bulk material.
Various conveyors are provided that extend along the outrigger and down the pendant arm as described in "Schiffsentlader nach dem Screw-Conveyor-Prinzip bieten gute Restenladung" (Fordern und Heben; 1987, no. 6), German 3,636,833 of Oy, European 0,242,193 of Addicott, German 4,208,653 of Grathoff, European 0,056,474 of Blattermann, German 2,414,583 of Riboulet, German 2,523,948 assigned to Fordertechnik Hamburg Harry Lassig, and German 2,740,698 of Chever. Various combinations of bucket, screw, and belt conveyors are proposed.
As a rule these unloaders are custom made for the specific application. So that they are quite expensive and complex. Furthermore it is very rare for an unloader to be set up for loading bulk material into a ship or other container also, as the extra equipment is often excessively complex. Any dual-purpose loader/unloader is normally extremely expensive and hard to use for any of its functions.